ANATOMY OF THE HORSE. 31 



ANTERIOR MAXILLARY BONES. 

 (OSSA MAXILLARIA ANTERIORA.) 



Situntiou. Supero-anterior and antero-lateral parts of the face. 



Form— Irregular ; consisting of a broad, thick portion or base, 

 turned forwards, from which is sent off a thin flexible plate ; and 

 a narrow, elongated, tapering portion, turned backwards. 



Division — Into three surfaces and three borders. 



Surfaces. The superio?- or nasal surface is smooth, convex, 

 and oblong; more extensive externally than internally; and free 

 from all connection, it forming one side of the nasal space, in cor- 

 respondence with its fellow. Outwardly, it affords attachment to 

 the nasalis brevis labii superioris; inwardly, it is invested by the 

 pituitary membrane. The inferior or palatine sinface is vaulted, 

 it contributing to the formation of the palate : within it, of an oval 

 form, is the interdental space, which is occupied by two thin 

 flexible plates, the palatine processes, denticulating along the sides 

 with each other. In the side of the bone is a deep hollow, for the 

 reception of that portion of the superior maxillary bone which holds 

 the tusk ; and the remainder of the surface, posteriorly, is arti- 

 culated with the same. The anterior or labial surface is broad, 

 smooth, and convex, and gives attachment to the depressor labii 

 superioris, the gums, and the membranous and cellular tissue en- 

 tering into the composition of the upper lip. 



Borders. The anterior border is broad and curved, and is 

 composed of two laminee, formed apart and divided by five trans- 

 verse septa into six conical alveolar cavities, for lodging the inci- 

 sive teeth. The posterior border is narrow and sloped off, and 

 denticulates with the nasal bone. The internal border is broad, 

 quadrilateral, and curved, and denticulates with its fellow, forming 

 thereby the superior maxillary symphysis, through which runs the 

 foramen incisivum, for the transmission of the palatine arteries. 



Particularities. These bones are remarkable for smoothness 

 of surface, and closeness and hardness of texture. They are united 

 at the symphysis, in the young subject by a fibrous cartilage, in 

 the adult by osseous matter; so that, by maceration, they are 

 separable in the one instance, inseparable in the other. Their 

 alveolar cavities increase in number and size with the age and 

 growth of the animal. 



Connection — With the superior maxillary and nasal bones, and 

 with each other. 



malar bones, (ossa malarum.) 

 Situation. Antero-external part of the orbit. 

 Figure— Irregularly triangular, presenting a broad basis for- 

 wards. 



